The disorders noted above include, among others, asthma and other inflammatory diseases of the pulmonary system like allergic rhinitis, chronic obstructive pulmonary disease, respiratory syncytial virus and smoker's emphysema where the methods and compositions described herein are useful. Furthermore, the compositions and methods are particularly useful in treating the underlying pathological changes in the airways associated with these diseases such as basement membrane thickening, cell hypertrophy and hyperplasia, inflammatory cell influx, and other tissue remodeling. Other inflammatory conditions, including, for example, rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, conjunctivitis, psoriasis, scleroderma, and related diseases can be treated with the compounds and methods described herein.
To better understand the invention, the following brief description of mast cell mediated disease, particularly asthma, is provided. Human asthma is a complex inflammatory disease. Genetic susceptibility and repeated allergen exposure from a variety of sources lead to allergen sensitization that, via IL-4 production from T-cells and mast cells, can ultimately induce B-cell derived IgE levels that are significantly elevated over normal levels. Subsequent exposure to allergen coupled with these newly elevated IgE levels can activate the FcERI high affinity IgE receptor on the surface of mast cells and other pro-inflammatory cells in the lung to induce degranulation/activation and thus trigger a cascade of inflammatory responses. This early phase of the response is characterized by severe bronchoconstriction that reaches its peak at about 15 minutes followed by a recovery of several hours. Many pre-formed substances are immediately released from the mast cell including histamine, heparin, cytokines (including, for example, IL-3, IL-4, IL-5, IL-6, and TNF-.alpha.), and proteases (including, for example, cathepsin G, chymase, carboxy peptidase A, tryptase). In relation to these other proteases, tryptase is released in very large amounts up to 35 pg per cell (see Caughey, Am. J. Physiol., 257, L39-46 (1989) and Walls in "Asthma and Rhinitis" 1995, pp. 801-824). Furthermore, tryptase is long lived, and has been shown to have a myriad of significant effects as a peptidase, protease and cytokine that intensify the inflammatory response. For example, tryptase can cause further mast cell degranulation to amplify the allergen response (see Molinari et al., J. Appl. Physiol., 79(6), 1966-70 (1995)) and induce eosinophil and neutrophil migration into the lung (see Walls et al., Int. Arch. Allergy Immunol., 107, 372-3 (1995)). Also, tryptase can inactivate fibrinogen to act as a local anti-coagulant and promotes plasma extravasation bringing more circulating cells and mediators into the lung (see Schwartz et al, J. Immunol., 135, 2762-7 (1985)). Further, tryptase can process high and low molecular weight kininogen to bradykinin and activates kallikrein to produce neurogenic inflammation (see Proud et al., Biochem. Pharm., 37(8), 1473-80 (1988); Walls et al., Biochem. Soc. Trans., 20, 260S (1992); Imamura et al., Lab. Invest., 74, 861-70 (1996)) while degrading neurogenic feedback mechanisms like the bronchodilatory neuropeptides (for example, VIP, peptide histidine methionine and peptide histidine isoleucine) and further promote mucous secretion and bronchoconstriction (see Tam and Caughey, Am. J. Respir. Cell Mol. Biol. 3, 27-32 (1990)). Tryptase can amplify the effects of histamine to further enhance bronchoconstriction (see Molinari et al., J. Appl. Physiol., 79(6), 1966-70 (1995); Sekizawa et al, J. Clin. Invest., 83, 175-9 (1989); Johnson et al., Eur. Respir. J., 10, 38-43 (1997)). Tryptase is a mitogen/activator of fibroblast (see Ruoss et al., J. Clin. Invest., 88, 493-9 (1991); Gruber et al., J. Immunology, 158, 2310-17 (1997)) and bronchial smooth muscle cells which can contribute to airway hyperresponsiveness to the lung as seen in a variety of pulmonary disorders (see Brown et al., Chest, 107(3), 95-6S (1995); Caughey et al., Am. J. Respir. Cell Mol. Biol., 13, 227-36 (1995)). Further, tryptase is a mitogen for airway epithelial cells and induces IL-8 and ICAM-1 expression (see Cairns and Walls J. Immunology, 156, 275-83 (1996)) and recently tryptase has been shown to activate cellular receptors (see Molino et al., J. Biol. Chem., 272(7), 4043-49 (1997)).
Following this early mast cell degranulation and release of tryptase, the activation of the arachidonic acid cascade resulting in the production of lipid mediators, such as the leukotrienes (LTD4, LTC4, LTE4, LTB4), the prostaglandins (PGD2) and platelet activating factor (PAF), occurs several minutes later. Six to twelve hours after initial allergen exposure, a late phase inflammatory response takes place in which bronchoconstriction is again visited upon the asthmatic. By this time the mast cell has begun to produce protein mediators like the cytokines (IL-1,3,4,5,6), chemokines (IL-8, MIP-1a) and growth factors (GM-CSF). This late phase response is associated with a significant influx of inflammatory cells, most notably eosinophils, neutrophils, and lymphocytes, into the lung tissue and airway space. These cells are activated and release even more mediators which can contribute to the significant tissue damage and development of hyperresponsiveness seen in chronic asthma.
The various activities of tryptase contribute to the early and late phase bronchoconstriction as well as to the development of airway hyperresponsiveness, a hallmark of asthma. Furthermore, in chronic asthma and other long term respiratory diseases, these activities cause profound changes to the airway such as desquamation of the epithelial lining, fibrosis and thickening of the underlying tissues. These changes are not treated by present therapeutics.
Tryptase can be detected in a variety of biological fluids and recently tryptase's relatively long biological half-life (vis a vis histamine) has become appreciated and clinicians now use circulating levels of tryptase as a marker of anaphylaxis (see Schwartz et al., N. Engl. T. Med., 316, 1622-26 (1987)). Elevated levels of tryptase can be detected in lavage fluid from allergen challenged atopic asthmatics as well as in cigarette smokers, where there is significant lung damage (see Castells et al., J. Allerg. Clin. Immunol., 82, 348-55 (1988); Wenzel et al., Am. Rev. Resp. Dis., 141 563-8 (1988); Kalenderian et al., Chest, 94, 119-23 (1988)).
Tryptase can process prostromelysin to mature stromelysin (MMP-3) which can further activate collagenase (MM-1). Thus tryptase could play a significant role in the tissue remodeling of various pulmonary disorders (most notably asthma) but also in rheumatoid and osteo-arthritis.
Tryptase is stored in the mature form as a homotetramer within the secretory granules of the mast cell and probably is held in an inactivated form by the low pH of this intracellular media. When released it is stabilized by interactions with heparin. This unique assembly of 4 catalytically active subunits could also be considered to be a dimer of dimers because computational models indicate that two adjacent active sites may face one another.
Being a member of the tryptic-like serine protease family, human tryptase prefers an arginine or lysine in the P1 subsite of a substrate. Because of this well recognized preference for basic residues at S1 there have been reports of inhibitors that incorporate physiologically protonated basic chemical moieties. (See, for example, benzamidines (see Caughey et al., J. Pharm. Exp. Therap., 264, 676-82 (1993); Tidwell, et al., J. Med. Chem. 21(7), 613 (1978); Dominguez et al., WO 9801428 and references cited therein)); benzguanidines, benzylamines (see Rice et al., WO 9609297); and, modified peptides incorporating an arginine (see Spear et al., WO 9420527)). (See also Lum, e a., WO 95/32945 (based on U.S. Ser. No. 08/252,099, filed Jun. 1, 1994, now issued as U.S. Pat. No. 5,656,660 (granted Aug. 12, 1997)); Neises et al., U.S. Pat. No. 5,391,705 (granted Feb. 21, 1995); Neises et al., U.S. Pat. No. 5,498,779 (granted Mar. 12, 1996); Neises et al. EP A 0504064 (published Sep. 16, 1992); Powers et Al., U.S. Pat. No. 4,954,519 (granted Sep. 4, 1990); Von der Saal et Al., Wo 94/27958 (published Dec. 8, 1994) and Spear et al., U.S. Pat. No. 5,525,623 (granted Jun. 11, 1996)).